The present invention is related to the invention disclosed in U.S. Pat. No. 4,093,516 to Long, issued Jun. 6, 1978, the specification of which is incorporated by reference.
The typical process of cleaning crude sewage involves filtration. The filtration process results in two separate parallel flows, one of which consists of sediment, and the other of filtrate. The filtrate is then aerated by air or oxygen in order to oxidize organic contaminants and is then allowed to settle for a period of time. Formed sediment is mixed with sediment collected after preliminary filtration and then converted into liquid fuel. Settled water from the filtrate is decanted and sterilized with receiving treated water. But, the preliminary filtration and subsequent aeration leads to increasing the concentration of dissolved and fine suspended substances which cannot be separated easily from water in the following steps of cleaning.
In U.S. Pat. No. 5,514,282, to Hibbard et all., issued May 6, 1996, solids contained in wastewater are separated by air flotation by means of adding some coagulators, for example, iron salts and polymeric flocculates. In addition, after the flotation process wastewater is cleaned by multistage filtration using first a fine filter and then an ultrafilter. However, treated water needs additional cleaning before it may be used for domestic consumption because it contains too many dissolved contaminants.
In U.S. Pat. No. 5,120,435, to Fink, issued Jun. 9, 1996, wastewater is treated with preliminary separation from solids. This process results in increasing the concentration of dissolved and fine suspended substances in treated water. Therefore, in previous patents the treated water requires additional complicated cleaning processes before use for domestic consumption.
In conclusion, a need exists for developing an economical and effective domestic sewage cleaning system which produces treated water which is pure enough to be used for domestic consumption.